Physical layer – general description, characteristics

Switching
Switching is a mechanism by which data/information sent from source towards destination which are not directly connected. Networks have interconnecting devices, which receives data from directly connected sources, stores data, analyze it and then forwards to the next interconnecting device closest to the destination.
Functions of Physical Layer

• The work of the physical layer is that this upper layer converts all the information received from the data link layer into signals and transmits it from one computer to another using a communication medium such as a wire or wireless medium.
• It controls the speed of transfer of data, means that the physical layer is responsible for controlling how many bits of information per second the machine has to transfer.
• This layer is establish a common connection between the sender of the information and the receiver of the information, so that the information can be passed to the receiver without any problems.

• How to organize different types of devices to connect to the network means to choose from the network topology such as Mesh, Star, Ring and Bus to establish the connection in the network. It helps in deciding.
• Signals are mainly of two types, Analog Signals and Digital Signals, the decision of which one to use to transfer information is also taken by the physical layer.
• There are a total of three types of transmission modes in computer networks such as Simplex, Half Duplex and Full Duplex.
• It also avoids conflicts between information flowing in the network due to data packets becoming undeliverable.

Fiber-Optic Cable differs from those previously discussed because it transmits bits as light signals instead of electrical signals. Fiber is desirable because the signal it carries it not subject to EMI. It can be used to solve problems in LANs or Campus Area Networks where offices or buildings are not all connected to a single ground source and equipment connected to a copper wire network would be fried by normal differences in ground associated with weather. Fiber supports very high bandwidths, makes up the 'backbone' of The Internet, and most long-distance carriers today depend on it.
It is similar to copper cabling in that it has a conductor, insulator, and outer sheath. The sheath must meet codes depending on whether the cable is in a plenum or not. The conductor is a relatively fragile glass fiber which is usually coated with a plastic buffer. The buffer's material depends on where the fiber-optic cable is run. Fiber-optic cabling is run indoors and outdoors and the cable's specification must be appropriate for the application. Kevlar fibers, or other materials, surround the buffered fiber and serve to strengthen and stiffen the cable and protect the delicate fiber conductors.